This invention relates generally to ducting which is used in ducted heating systems and air conditioning systems, and particularly relates to an improved duct joiner for joining an end portion of a hollow air duct either to another air duct or to another part of a heating or air conditioning system, such as an air diffuser or a grille outlet. The invention also relates to a method of manufacturing such a duct joiner.
It is known to use duct joiners to join together ducts in a ducted heating or air conditioning system by placing a duct over a neck portion of the duct joiner and taping the duct to the duct joiner. This form of connection can easily break, is time consuming when installing ducts, and does not provide an effective sealed connection. This last deficiency results in an inefficient air conditioning system since a substantial amount of the conditioned air does not reach the space that requires the air conditioning but is lost through the connections of the duct and duct joiners.
It is therefore desirable to provide an improved means for connecting a duct to a duct joiner in which one or more of the disadvantages of known connecting means are overcome. It is also desirable to provide a duct joiner which is relatively inexpensive and easy to manufacture and use.
The duct joiner of the present invention is particularly, but not exclusively, applicable for use in joining flexible ducting having a generally cylindrical cross-section, the ducting being produced by encapsulating a helically formed wire support in a flexible polymeric substrate material.
According to one aspect of the invention, there is provided a duct joiner for air ducting, the joiner having at least one tubular neck portion formed of resilient plastics material having a first open end, a second end and a through channel allowing the passage of air from one of the ends to the other, the tubular neck portion having a plurality of annular grooves formed therein, a first groove of the annular grooves being disposed closest to the first open end and provided with a plurality of resilient projections extending out of the first groove and adapted to engage with the internal surface of an end portion of a hollow air duct fitted on the joiner, a second groove of the annular grooves being adapted to receive a sealing ring of relatively soft material which extends out of the second groove for sealing engagement with the internal surface of the end portion of the duct, wherein the outer surface of the tubular neck portion between the first and second grooves is a ramp surface being of lesser diameter adjacent the fist groove and of greater diameter adjacent the second groove, the ramp surface assisting in assembly of the end portion of the hollow air duct on the duct joiner.
In use of the duct joiner, the tubular neck portion is inserted into the end portion of a hollow air duct which is of slightly greater diameter than the diameter of the tubular neck portion. The internal surface of the duct engages first with the resilient projections which flex to allow the duct to pass over the projections. The duct end then engages with the ramp surface which slightly expands the internal diameter of the end portion of the duct to assist in further movement of the duct over the resilient projections and the sealing ring received in the second groove.
In a preferred form of the invention, the second groove for the sealing ring is disposed between the first groove and a third annular groove which is also provided with a plurality of resilient projections which extend out of the further groove to provide further means for engaging the internal surface of the end portion of the duct. Preferably, the outer surface of the tubular neck portion between the second groove and the further groove is also a ramp surface, the ramp surface being of lesser diameter adjacent the further groove and of greater diameter adjacent the second groove. The design of the ramp surfaces is such that a firm sealing contact is achieved between the internal wall of the duct and the sealing ring.
The preferred arrangement of the sealing ring in the second groove between the resilient projections extending out of the first groove and the further groove provides a very effective sealed connection which is easy to assemble and relatively easy to disassemble. Further, the duct joiner of the present invention does not require separate fastening clips or fastening tape to secure the duct joiner to the end of an air duct.
Preferably, the duct joiner has an annular flange provided at the end of the tubular portion remote from the first open end which can be used as an abutment or stop for the end of an air duct fitted on the tubular neck portion of the joiner.
The duct joiner may have a single neck portion and an air outlet portion providing an exit channel through which air can blow into a room or the like. Alternatively, a duct joiner in accordance with the invention may have a plurality of neck portions, each having the grooves provided with resilient projections and a sealing ring for joining one duct to at least one other duct. For instance, a duct joiner may be provided for joining ducts of different diameters, the joiner having a first generally cylindrical neck portion of one diameter and a second generally cylindrical neck portion of another diameter, each neck portion having the grooves with resilient projections and a sealing ring. Also, a duct joiner having at least one branching neck portion in addition to a main neck portion or neck portions may be provided for connecting a branch duct to a main duct.
In a preferred method of manufacture, the duct joiner in accordance with the first aspect of the invention is formed by moulding the duct joiner in at least two parts with complementary interengaging formations provided on side edges of the parts, and the side edges of the parts are joined together by the complementary interengaging formations.
According to another aspect of the invention there is provided a method of forming a duct joiner having at least one tubular neck portion with annular grooves for resilient projections and for a sealing ring, said method including the steps of:
forming the duct joiner in at least two parts with complementary interengaging formations provided on side edges of the parts; and
joining the side edges of the at least two parts together by means of the complementary interengaging formations.
Preferably, the interengaging formations provided on the side edges of the joiner parts comprise a recess or mortice in one of the parts and a complementary projection or tenon on the side edge of the other part.
In a particularly preferred embodiment of this aspect of the invention, there is provided a branch duct joiner formed in two parts joined together in the manner above and having first and second tubular neck portions sharing a common longitudinal axis and provided on each side of a central section, the central section having a cylindrical sideways extension adapted to be joined to a tubular branching neck portion.